Artifacts are any unwanted changes that occur in an image that are caused by various factors within a DSLR or point and shoot camera. This article looks at the most common artifacts found in digital photography.
- Blooming. Pixels on a DSLR sensor collect photons, which are converted into an electrical charge. However, the pixels occasionally can collect too many photons, which causes an overflow of electrical charge. This overflow can spill onto existing pixels, causing overexposure in areas of an image. This is known as blooming. Most modern DSLRs have anti-blooming gates which help to drain away this excess charge.
- Chromatic Aberration. This occurs most frequently when shooting with a wide-angle lens, and it is visible as color fringing around high contrast edges. It is caused by the lens not focusing wavelengths of light onto the exact same focal plane. It can be corrected by using lenses that have two or more pieces of glass with different refractive qualities.
- Jaggies / Aliasing. This refers to the visible jagged edges on diagonal lines in a digital image. Because pixels are square (not round), a diagonal line consists of a set of square pixels, which can look like a series of stair steps when the pixels are large. Jaggies disappear with higher resolution cameras because the pixels are small. DSLRs naturally contain anti-aliasing abilities, as they will read information from both sides of an edge, thus softening the lines. Sharpening in post production will increase the visibility of jaggies.
- JPEG Compression. JPEG is the most common photo file format used to save digital photo files. However, JPEG gives a trade-off between image quality and image size. Every time you save a file as a JPEG, you compress the image and lose a little quality. And each time you open and close a JPEG (even if you perform no editing on it), you still lose quality. If you plan to make a lot of changes to an image, it's best to save it initially in an uncompressed format, such as PSD or TIFF.
- Moire. When an image contains repetitive areas of high frequency, these details can exceed the resolution of the camera. This causes moire, which looks like wavy colored lines on the image. Moire is usually eliminated by higher resolution cameras. Those with a lower pixel count can use anti-aliasing filters to correct the problem of moire, although they do soften the image.
- Noise. Noise shows up on images as unwanted or stray color specks, and noise is most commonly caused by raising the ISO of a camera. To learn more about noise in photography, just click the link.